In men, the risk of a heart attack greatly increases after 45, says Dr. John Harper, chair of cardiology on the medical staff at Texas Presbyterian Hospital Dallas. And the risk just keeps increasing with age. Approximately 85 percent of those who die from heart disease are over 65, according to American Heart Association statistics.

What we do know is that heart disease is the leading cause of death in the U.S. for both men and women, according to the Centers for Disease Control and Prevention. Approximately 600,000 people, or one in four deaths, are from heart disease each year.

More than 1.2 million heart attacks occur each year in the U.S. and it’s estimated that 460,000 of these are fatal, according to the National Institutes of Health. Just like Gandolfini, approximately 300,000 people die annually before they can receive medical treatment; medical professionals tried to revive Gandolfini unsuccessfully for 40 minutes before declaring him dead.

While there are no definitive numbers, it is not rare for the first symptom to be the last.

That's why Dr. Harper says recognizing the signs and symptoms and doing everything you can to prevent a heart attack is important.

Here's how he advises doing that:

Know your risk factors: High blood pressure, high cholesterol and smoking are key risk factors for heart disease. Your risk is also elevated if you have diabetes, are overweight or obese, have a poor diet, smoke, are physically inactive or drink alcohol excessively.

Know the signs of a heart attack: chest discomfort that can feel like painful pressure or squeezing; pain or discomfort in other parts of the body such as arms, jaw, back neck or stomach; shortness of breath; dizziness; breaking out in a cold sweat; nausea. Women may have atypical symptoms, such as an indigestion-like feeling and extreme fatigue.

Act IMMEDIATELY: Most people don’t recognize these symptoms until it is too late, Dr. Harper says, adding: "If you or someone you know experience these symptoms you should immediately call 911 or have someone nearby do so. Don’t wait! Then locate an AED and begin CPR. Continue to do this until EMS personnel arrive on-scene."